The inspection of specimens which have been sectioned or ground to produce a surface passing through a region of interest, in many cases a defect in a device, previously required that the specimen be mounted on a support such as a microscope stage and inspected either from only one direction or that the item be removed, re-attached, and then repositioned within the view of the microscope for inspection from a second viewing direction. In most cases, this specimen removal, re-attachment and subsequent reposition within the field of view of the microscope is laborious and time consuming. For example, if an electronic chip which typically comprises a ceramic chip and/or a ceramic substrate, each containing a large number of insulating and conducting deposits or layers, is suspected of being defective, and an optical inspection reveals a particular area to be more closely considered, the electronic chip then is sectioned or successively ground to different planes. The planes may be perpendicular or beveled at an angle to the plane of the surface through which the optical inspection has occurred to locate the potential defect. As the potential defect is sectioned, it is often desirable to observe the area of interest from angles other than a top surface.
After the area of interest has been sectioned either on a plane acutely angled or perpendicular to the plane of the top surface of the device, then it is extremely difficult to identify again the region of interest; that region viewed from a different direction may appear very different than the originally viewed area. Accordingly, it is extremely time consuming and laborious to re-locate and re-identify the region to be inspected.
An alternative to the removal, re-attachment, reinstallation and relocation of the specific area being inspected, as described above, is the use of two microscopes disposed for viewing at an angle to each other such that a selected area may be inspected from one direction through one microscope and then the area inspected from another direction through the second microscope. The significant disadvantage to this technique over and above a requirement of two microscopes and expensive redundancy in equipment, is that the two microscopes must be positioned relative to each other with extreme precision, in order for both to be able to view the region being inspected.
The foregoing approach to remove the sample, move and re-attach it on the holder and then to re-install the sample only provides the viewer with two possible views of the region being inspected. The first position being that where the defect was originally identified and exposed; the second position being the position into which the sample has been moved following its removal, re-attachment and re-installation into the microscope viewing assembly. These two positions may not provide the best view of the area being inspected in order to identify and to analyze that region. If that region is a defect, it may be particularly desirable to view the region from a plurality of closely associated or varying positions. Whenever it is necessary to view the sample in a multitude of different positions, each requiring the removal and reposition of the sample on to the holder and the subsequent re-installation of the holder into the optical inspection assembly, a complete analysis of the area being viewed becomes too expensive in terms of time and effort as well as being a slow and laborious process.
The disadvantages of this approach prevent the efficient inspection of selected regions of samples from a plurality of different angular views.